Enrique Raba hurt his knee and at points was carried by teammates. (Evy Mages/For The Washington Post)

As you were getting ready for bed Saturday night, 20 men and one woman were standing in Rock Creek in shorts and T-shirts belting the lyrics to the “SpongeBob SquarePants” theme song into the moonless night. That is, when they weren’t face down in the shallow water doing push-ups, or on their backs doing flutter kicks, or crawling on their bellies from the creek into the mud at the water’s edge and back in again — all with 40-pound packs on their backs.

That was in the first hour or so of their excruciating 12-hour ordeal on the D.C. streets Saturday night and Sunday morning, a sometimes strange journey through Georgetown, Dupont Circle, Foggy Bottom and the Mall as the city partied and slept.

It’s called the “GoRuck Challenge”, a military-style endurance event led by former Special Forces personnel that stresses toughness and teamwork in the face of almost insurmountable challenges. It is less extreme than some events in the growing field of obstacle racing, such as the annual Spartan Death Race­, ­but it’s much longer and more difficult than events such as Run Amuck and Warrior Dash.

In fact, it’s not a race at all, and, unlike the Death Race, organizers aren’t trying to force participants to quit. (GoRuck hosts other events that whittle away all but the toughest of the tough.) Only two people dropped out of this weekend’s challenge, both in the first hour, when they realized GoRuck was much more than they were prepared for. Both were older guys. One of them was me.

The rest appeared to be in their 20s and 30s, almost all visibly strong and fit. A few were military or ex-military. A large contingent from Balance Gym’s CrossFit and boot camp classes signed up together. One trio came down from northern New Jersey, though GoRuck is offered just about everywhere.

Participants will walk 20 miles, bear crawl, carry their buddy etc., while wearing 40 lbs back packs. (Evy Mages/FOR THE WASHINGTON POST)

“If I can get them to stop arguing, put their differences aside, I succeed in my eyes,” said the leader, or “cadre,” of GoRuck Class 253, a 26-year-old former Green Beret named Chris, who asked that I not use his last name because he might return to active duty someday. He added, “The teamwork, it comes. It naturally happens. I’m just here to coordinate and add some stress.”

At that he is a practiced master. He hectored appointed team leaders and tightened the screws when participants believed they had reached the point of exhaustion. One of his favorite tricks as the night wore on was to add time limits to challenges and mete out penalties if the entire team didn’t hit his deadlines.

Load up and haul out

The night begins at 10 p.m. in Georgetown’s Montrose Park. Participants, who paid $100 or more, depending on when they signed up, arrive carrying backpacks (“rucks” in military parlance) that contain six bricks wrapped in duct tape, along with water, food, gloves and some dry clothing. Chris confiscates watches and cellphones and bans the headlamps each person was instructed to bring. This class will be conducted in complete darkness.

The group is also carrying “team weight” — a box that contains two 25-pound dumbbells and, separately, another 25-pound weight plate — that is a collective responsibility. For the next 111 / 2 hours, no ruck or team weight can touch the ground. “If a ruck touches the ground,” Chris tells them as they stand in two lines in the darkness of Montrose Park, “I’m going to lose my mind.”

I take him at his word. Chris led Class 248 on Friday night and says that by the end of our excursion he will have been awake about 50 straight hours. He spends the night gulping Red Bull, a habit he picked up in Iraq, the way the rest of us drink water.

After a one-kilometer “bear crawl” — hands and feet must touch the ground at all times — each person carries a buddy down a steep hill to the creek. Wet and filthy from the “SpongeBob” exercise, they hike out of the creek and back up a hill.

Then the fun begins.

Chris tells them to wrestle a fallen tree trunk up the bank of a steep ravine. They succeed, but he is unhappy with the one they have chosen, so they must find another. Again they succeed. Then he tells them to hoist the log, which weighs perhaps 1,500 pounds, and carry it out of the park.

It is 12:30 a.m. For the next two hours, in one of the more bizarre culture clashes Washington has seen, the team carries a rotting tree trunk through some of the city’s wealthiest neighborhoods, down the slumbering streets of Georgetown and into the West End. Revelers, dressed in their Saturday night party clothes, stop to cheer, gawk and ask about the 21 soaked, dirty people carrying the log, stump and all.

“What is it, a frat thing?” one man asks outside the Caucus Room restaurant in the Westin Hotel on M Street as he stops to snap a photo with his cellphone.

It is not a frat thing. It’s “to see if I can do it, to see what I’m made of,” said Joshua Hill of Rockville as the team rested, the tree trunk on the ground, outside a gas station mini-mart across from the Ritz-Carlton condos. “My family, my friends, think we’re insane. And to tell the truth, they’re probably right.”

Somewhere along the way, Chris has produced a huge American flag on a long steel pole, which requires two or three people to carry. Despite the obvious toll it is taking, however, the team is adapting to its task. Chris wants them to realize they would be more efficient with fewer people carrying the trunk and fresh bodies rotating in, but they never figure that out. So at 2:20 a.m., in the wooded fringe behind a school at 25th and N streets, he introduces their next foe: a fat slice of tree trunk that is nearly as heavy but only about five feet long.

They must carry it to the Washington Monument.

The log is too short for the whole team to lift. Someone finds two strong steel poles that are perhaps seven feet long. They balance the tree section on the two poles, and with four of the shortest, strongest people on each one, they can barely lift it to their waists. But it is so heavy that some of them don’t last long as the team begins to creep en masse toward the Mall. They don’t dare put it down; they’d never be able to raise it again.

They devise a rotation, almost like two volleyball teams, moving briefly rested arms and legs into position on the two poles as each man or woman gives out. They reach the monument at 4:20 a.m. and collapse in exhaustion.

Chris allows them 20 minutes to rest, rehydrate and use the bathroom. They drop the short log in a wooded area, trading it for an empty wooden box Chris has found. He announces that they must run to the Lincoln Memorial in 10 minutes, still carrying the 75 pounds of team weight, the flag and now the empty box. They make it, give or take a few seconds.

He tells them to bear-crawl, backward, up the steps of the memorial.

The 40-pound packs slide onto their heads and necks as they inch painfully, rear ends first, up the steps. Even Chris has a few words of regret for the misery he is inflicting. There will be more rest at the top.

The task grows tougher

At 6 a.m., as first light is breaking over the Capitol, early-morning joggers take in the sight of the bedraggled team doing push-ups at the base of the memorial, warming up for the run to Georgetown’s Washington Harbour.

But there is a problem. One man, Enrique Raba, has injured his knee. Chris tells them to deal with it, but they are unsure how. Raba limps badly, trying to keep pace with the team as it hustles down the Potomac past the Kennedy Center and the Watergate. Two guys try to support him. Then they carry him. Finally they reach the fountain at the end of their run.

As the sun starts to rise, Chris orders them into the water for burpees and flutter kicks.

Soaked again, they head up the hill to the famous staircase on M Street where a scene from “The Exorcist” was filmed. Along the way, Chris finds a pair of two-by-fours and they assemble a stretcher out of shirts slung between the lengths of wood. Now four to six of them are devoted to carrying their injured comrade, two or three more are on the flag and the team weight is still being passed around.

A steel bar connects the stairs and the adjacent building, and Chris tells the team they must collectively do 201 pull-ups. They try, putting the strongest first, but in their exhaustion, they don’t come close. They ask for their punishment early.

Chris tells them they must carry several team members, plus Raba, the flag, the team weight and all the rucksacks, up the stairs. Then they must run down to Rose Park for a game of baseball.

This is no ordinary contest. He divides them into teams of 10 members each, with Raba sitting this one out. Two at a time, they begin at home plate and round the bases, one heading to first base, the other to third. Running is, of course, prohibited. They must high-crawl the first leg on their hands and knees, crab-walk the second, bear-crawl the third and high-crawl home.

Chris tells them that when their paths cross, they can do anything they want to impede their opponents, and team members can also stop or aid anyone nearing home plate. The result is a wild, free-for-all wrestling match in the red-brown dirt of the basepaths before amused Dupont Circle dog-walkers shortly before 8:30 a.m.

Caked with dirt, sweating and exhausted, they begin a sprint uphill back to Montrose Park. But as they start to pick up speed, Chris tells the team leader that snipers have picked off one, then a second member of the group. They must carry the two men back up the hill — along with everything else.

They are almost out of able bodies, but they somehow manage to lug their dead back to the park, where Chris arranges the group in two lines for push-ups on the spot where the night began 111 / 2 hours earlier. “Let’s go,” he orders, and they drop to the ground shortly before 9:30 a.m., wet, filthy and still wearing their 40-pound packs.

“Are you kidding?” Chris asks with a huge smile. “You’re done.”

They’re not quite sure whether Chris has one more trick in store for them. But they rise slowly and begin to hesitantly applaud before breaking out in grins, hugging and high-fiving each other until Chris assembles them in a line and distributes the “GoRuck Tough” patches they have earned. He has a handshake, a bro-hug and a point of praise for each, reserving special congratulations for two men who have completed their second challenge and Rachel Dodd, a Marine who has survived with 20 male comrades. They take a group photo before Chris’s huge U.S. flag.

“You did Chris’s class,” he tells them. “And I’m the hardest f-----g cadre there is.”

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